MXPA01002430A - Microbial process for the preparation of acetic acid as well as solvent for its extraction from the fermentation broth - Google Patents

Abstract

A modified water-immiscible solvent useful in the extraction of acetic acid from aqueous streams is a substantially pure mixture of isomers of highly branched di-alkyl amines. This solvent is substantially devoid of mono-alkyl amines and alcohols. Solvent mixtures formed of such a modified solvent with a desired cosolvent, preferably a low boiling hydrocarbon which forms an azeotrope with water are useful in the extraction of acetic acid from aqueous gaseous streams. An anaerobic microbial fermentation process for the production of acetic acid employs such solvents, under conditions which limit amide formation by the solvent and thus increase the efficiency of acetic acid recovery. Methodsfor the direct extraction of acetic acid and the extractive fermentation of acetic acid also employ the modified solvents and increase efficiency of acetic acid production. Such increases in efficiency are also obtained where the energy source for the microbial fermentation contains carbon dioxide and the method includes a carbon dioxide stripping step prior to extraction of acetic acid in solvent.

Description

MICROBIAL PROCEDURE FOR THE PREPARATION OF ACETIC ACID AS WELL AS SOLVENT FOR THEIR EXTRACTION OF THE BROTH OF FERMENTATION This invention has been partially sponsored by donations from the Department of Energy of the United States, Cooperative Agreement No. DE-FC02-90CE40939. The government of the United States has interest in this invention.

FIELD OF THE INVENTION The present invention relates generally to improved methods for the microbial production of acetic acid. More particularly, the invention relates to the extraction of acetic acid from aqueous streams and the microbial fermentation of desirable chemicals from gas streams, such as waste gas streams, industrial gas streams or gas streams produced by gasification of carbonaceous materials.

BACKGROUND OF THE INVENTION Methods have been carried out, at laboratory bench scale, for the anaerobic fermentation of carbon monoxide and / or hydrogen and carbon dioxide to produce acetic acid, acetate salts or other products of commercial interest, such as ethanol. See, for example, Vega et al. (1989) Biotech. Bioeng .. 34: 785-793; Klasson et al. (1990) Appl. Biochem. Biotech., 24/25: 1, Vega ef al. (1989) Appl. Biochem. Biotech., 22/21: 781-797; and Klasson the al. (1992) Enz. Microbe. Tech .. 19: 602-608. among others. More recently, the present inventors have discussed large-scale methods for the fermentation of industrial gas streams, particularly waste gas streams, to form products for commercial use, using methods that employ fermentation of the gas stream, a nutrient medium. aqueous and anaerobic bacteria or mixtures thereof in a bioreactor. See, for example, U.S. Patent No. 5,173,429; U.S. Patent No. 5,593,886 and International Publication No. WO98 / 00558, incorporated herein by reference. According to the prior art of the aforementioned inventors, such a large-scale process involves the following summarized steps. Nutrients are continuously fed to a bioreactor or fermentor in which a culture, either single or mixed species, of anaerobic bacteria is found. A gas stream is continuously introduced into the bioreactor and retained in the bioreactor for a sufficient time to maximize the efficiency of the process. Waste gases containing inert and unreacted substrate gases are then released. The effluent is passed to a centrifuge, hollow fiber membrane or other solid-liquid separation device to extract the microorganisms that are entrained. These microorganisms are returned to the bioreactor to maintain a high concentration of cells that produces a higher reaction rate. Separation of the product (s) from the permeated or centrifuged material occurs by passing the permeated or centrifuged material to an extractor where it is contacted with a solvent, such as a dialkyl or trialkylamine in a suitable cosolvent, or tributyl phosphate, ethyl acetate, trioctylphosphine oxide and related compounds in a cosolvent. Suitable cosolvents include long chain alcohols, hexane, cyclohexane, chloroform and tetrachloroethylene. Nutrients and materials in the aqueous phase pass back to the bioreactor and the solvent / acid / water solution passes to a distillation column, where this solution is heated to a temperature sufficient to separate the acid and water from the solvent. The solvent passes from the column of distillation through a cooling chamber to lower the temperature to the optimum temperature for extraction, then back to the reactor for reuse. The acid and water solution passes to a final column where the desired final product is separated from the water and removed. The water is recirculated for the preparation of nutrients. In addition, a variety of acetogenic bacteria are well known to produce acetic acid and other commercially interesting products, when subjected to such fermentation processes, including novel Clostridi? M Ijungdahlii strains [See, for example, patents of United States Nos. 5,173,429 and 5,59 ^, 886, and international publication No. WO98 / 00558]. Despite such knowledge and such advances in the technique of microbial fermentation of a variety of gas streams, the production of acetic acid is limited by the acetic acid loading potential of the solvent used and by the degradation of the solvent as it travels through the production process, among other points. In view of the continually growing need to produce acetic acid, as well as to convert industrial waste gases into useful non-polluting products, there remains a need in the art for processes that are more effective in producing the desired commercial product and compositions that can enhance the performance of such methods.

BRIEF DESCRIPTION OF THE INVENTION In one aspect, the present invention provides a modified water-immiscible solvent useful in the extraction of acetic acid from aqueous streams comprising a substantially pure mixture of highly branched dialkyl amine (or secondary amines) isomers. This solvent can extract the acid in the absence of a cosolvent. In a preferred embodiment, this solvent is a modified form of Adogen 283® solvent [Witco Corp.] which is substantially reduced in its content of alcohols and monoalkylamines (or primary amines). In a modality "£ _ _--iii¿ £ £ £ £ í í« «« «« «« «« «« «« «« «« «« «« «« «« «« «« «« «« « -Nor S? wi,. , _. preferred, the solvent is further reduced in content (ie substantially purified) of trialkylamines (or tertiary amines). In another aspect, the invention provides a method for treating a solvent comprising alcohols, monoalkylamines, a mixture of dialkyl amine isomers and highly branched trialkylamines to improve their acetic acid extractability which comprises distilling substantially all alcohols and monoalkylamines from the solvent. In another embodiment, the method involves subjecting the distillate solvent to a second distillation to substantially eliminate all trialkylamines. In a still further embodiment, the invention provides a novel solvent / cosolvent mixture immiscible with water, useful for the extraction of acetic acid, preferably at concentrations of less than 10%, of an aqueous stream comprising a solvent immiscible with water, modified , previously described, useful in the extraction of acetic acid from aqueous streams comprising a substantially pure mixture of highly branched dialkyl amine isomers and a selected cosolvent. In a preferred embodiment, the cosolvent is a hydrocarbon having from 9 to 11 carbon atoms, hydrocarbon which forms an azeotrope with water and acetic acid. In yet another aspect, the invention provides a non-fermented process for obtaining acetic acid from an aqueous stream comprising contacting the stream with a modified solvent / cosolvent mixture as described above; extract the _ _. -_L ^ iS ^ t: ^ acetic acid from the aqueous phase to the solvent phase; and distilling the acetic acid from its mixture with the solvent at a temperature not exceeding 160 ° C. In a still further aspect, the invention provides a non-fermented process for obtaining acetic acid from an aqueous stream comprising contacting the stream with a solvent / cosolvent mixture as described above; extract the acetic acid from the aqueous phase to the solvent / cosolvent phase; and distilling the acetic acid from its mixture with the solvent / cosolvent at a temperature not exceeding 160 ° C under vacuum. In a further aspect, the present invention provides an anaerobic microbial fermentation process for the production of acetic acid, the method comprising the steps of (a) fermenting in a bioreactor an aqueous stream comprising a gas selected from the group consisting of carbon; carbon monoxide and hydrogen; hydrogen and carbon dioxide; in a mixture of nutrient with an acetogenic bacterium, thus producing a broth comprising acetic acid; (b) continuously extracting acetic acid from the broth with a modified solvent / cosolvent mixture as described above; (c) continuously distilling the product of (b) the acetic acid separately from the solvent at a temperature not exceeding 160 ° C, and (d) optionally recirculating the solvent and the broth through the bioreactor. The steps of extracting and distilling occur without substantially degrading the amine to an amide, thus enhancing the efficacy of acetic acid recovery from the broth.

In yet another aspect, the present invention provides a method for enhancing the recovery of acetic acid from a fermentation broth comprising an aqueous stream containing one or more of carbon monoxide; carbon dioxide and hydrogen; and an anaerobic, acetogenic bacterium and half nutrient; the method comprising contacting the stream with a solvent comprising the dialkylamine and a selected cosolvent; continuously extract the acetic acid from the stream in the solvent mixture and distill acetic acid from the solvent mixture under vacuum at a distillation temperature of less than 160 ° C thereof, without substantially degrading the amine to amide. In still another aspect, the invention provides an improved method for enhancing acetic acid recovery from anaerobic microbial fermentation of an aqueous stream comprising carbon monoxide; carbon monoxide and hydrogen; carbon monoxide, carbon dioxide and hydrogen, or carbon dioxide and hydrogen, wherein the method comprises the steps of contacting the fermentation product of the stream with a solvent immiscible with water; extract the fermentation product from the stream and distill the acetic acid from it. The improvement comprises employing as the solvent the modified solvent / cosolvent mixture described above and performing the distillation step at a temperature not exceeding 160 ° C without substantially degrading the amine to amide.

In a still further aspect, the invention provides an anaerobic microbial fermentation process (i.e. an extractive fermentation process) for the production of acetic acid which is effected without filtration or cell separation occurring prior to extraction. In one embodiment, this method involves providing in a fermentor an anaerobic acetogenic bacterium in a nutrient mixture and a water-immiscible solvent comprising a substantially pure mixture of highly branched dialkyl amine isomers with a selected cosolvent, for a sufficient time to acclimatize the bacteria to the solvent. A stream of gas comprising one or more of carbon dioxide, carbon monoxide and hydrogen is introduced into the fermenter and a fermentation broth is produced comprising the bacteria, the nutrient medium, the acetic acid, the solvent mixture. The fermentation broth containing the cells and the nutrient mixture are introduced to a sedimentation tank, where an aqueous phase containing the bacteria and the nutrient medium is deposited at the bottom of the tank of the solvent phase containing acetic acid, solvent and water, without filtration. The continuous distillation at a temperature not exceeding 160 ° C removes the acetic acid separately from the solvent. The step of distilling occurs without substantially degrading the amine to amide, thus enhancing the efficiency of the recovery of the broth. In still another aspect, the invention provides an anaerobic microbial fermentation process (ie, a direct contact extraction process) for the production of acetic acid, which does not involve filtration of the bacterial cells, the method comprising the steps of: a) fermenting in a bioreactor an aqueous stream comprising a gas containing one or more of carbon monoxide, carbon dioxide and hydrogen in a mixture of nutrient with an anaerobic acetogenic bacterium, thereby producing a broth comprising acetic acid, water and bacterial cells; (b) introducing a conventional extraction device, such as a column with either solvent or water as the continuous phase, (i) the broth without cell separation and (ii) a solvent mixture comprising a solvent immiscible with water modified useful in the extraction of acetic acid from aqueous streams comprising a substantially pure mixture of highly branched dialkyl isomers and a selected cosolvent, wherein a solvent phase containing acetic acid, solvent and water leaves the column separately from a phase aqueous comprising the bacteria and the nutrient medium; and (c) continuously distilling the solvent phase of (b) the acetic acid separately from the solvent at a temperature not exceeding 160 ° C. Steps (b) and (c) occur without substantially degrading the amine to an amide, thus enhancing the efficacy of acetic acid recovery from the broth. In still another aspect, the invention provides an anaerobic microbial fermentation process for the production of acetic acid, which comprises the step (s) of removing the dissolved carbon dioxide, and optionally dissolved hydrogen sulfide, from the fermentation before of the extraction. The steps of this procedure can include (a) fermenting in a bioreactor a stream of gas comprising one or more of carbon monoxide, carbon dioxide and hydrogen in a mixture of nutrient with an anaerobic acetogenic bacterium, thus producing a fermentation broth comprising acetic acid and dissolved carbon dioxide; (b) removing the carbon dioxide from the fermentation broth before extraction; (c) contacting the broth (b) with a solvent containing a dialkylamine, preferably the modified solvent / cosolvent mixture of this invention for a time sufficient to cause the formation of a solvent phase containing acetic acid, the solvent and Water; and (d) continuously distilling acetic acid from the solvent phase. The removal step of carbon dioxide / hydrogen sulfide can be carried out with a removal gas, by preheating the broth or by rapidly reducing the pressure of the fermentation broth. Other aspects and advantages of the present invention are more fully described in the following detailed description of the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a graph depicting a concentration of acetic acid (Hac) in solvent phase in g / l with respect to the concentration of Hac in aqueous phase in g / l for recovery procedures of acetic acid using 60% of the solvent modified, Adopt 283®LA in an azeotrope-forming solvent, SX-18. The experimental points are represented by triangles, the theoretical points by squares and the extraction coefficients (Kd). Figure 2 is a similar graph, except that the solvent mixture is 33% of cosolvent-modified solvent. Figure 3 is a schematic drawing of an exemplary apparatus assembly useful for the microbial fermentation of gases for the production of acetic acid, using the modified process step of the removal of carbon dioxide and hydrogen sulfide from the fermentation broth before extraction and also using only two distillation columns. See, for example, example 6. The auxiliary devices that control the temperature of several stages of this production process, such as cold water condensers, heat exchangers or steam, are identified in the figure. Figure 4 is a graph illustrating the temperature dependence of the rate of amide formation, according to the formula Y = kX, where is the amide concentration after 16 hours in percent by weight; X is the acetic acid in the material fed in percent by weight; and k is the rate constant for the amide formation. The formula for which the points on the graph are indicated is ln (k) = -9163.21 * (1 / T) + 27.41, where T is the absolute temperature in Kelvin. See, e.g., example 2 below.

DETAILED DESCRIPTION OF THE INVENTION The compositions and methods of the present invention are directed towards the improvement of processes for obtaining acetic acid from aqueous phases, including aqueous phases formed by fermentation processes. Thus, in one embodiment, acetic acid recovery processes are enhanced and acetic acid recovery is enhanced from dilute aqueous streams by employing in a distillation and extraction process a solvent comprising a mixture of highly branched dialkylamines and preferably a mixing of that solvent with a selected cosolvent in which limited degradation of solvent occurs. In another embodiment, the use of the same modified / cosolvent solvent mixture can enhance the acetic acid recovery of a microbial fermentation process for gas streams including the extraction / distillation steps. Other improvements in the recovery of acetic acid from the conventional fermentation processes provided by this invention involve eliminating the requirement for the separation of bacteria cells from the broth containing acetic acid in the process and / or replacing the use of an expensive extractor, in direct contact the bacterial cells with the selected mixture of modified / cosolvent solvent.

Still other improvements in the acetic acid recovery efficiency of the conventional fermentation process as well as the methods described below include removing the dissolved carbon dioxide and optionally the hydrogen sulfide from the fermentation before extraction.

A. The Modified Solvent and the Solvent / Co-solvent Mixture This invention provides a modified solvent and a solvent / cosolvent mixture that exhibit highly desirable characteristics for extraction of acetic acid from the aqueous phases containing the acid. This solvent and this solvent mixture are useful both for the extraction of acetic acid in non-fermentation processes as well as for the extraction of a fermentation broth that includes a microorganism, an aqueous medium and energy and carbon sources of the water streams. gas. 15 The desired solvent is defined (for abbreviation purposes, the "modified solvent") of this invention as a solvent immiscible with water useful in the extraction of acetic acid from aqueous streams comprising a substantially pure mixture of highly branched dialkyl amine isomers. Such a branched solvent preferably has a distribution coefficient Kd greater than 10 and more preferably greater than 15. This solvent can extract acetic acid in the absence of a cosolvent. By the term "substantially pure" is meant that the solvent contains more than 50% by volume of dialylamines and has a t? &eXiia. . * t. «wSt yes. .5? & amp; amp; amp; amp; amp; amp; amp; B & amp; amp; amp; amps; More preferably, the solvent contains more than 70% dialkylamines. In another preferred embodiment, the solvent contains more than 80% dialkylamines. In a still more preferred embodiment, the solvent contains between 80% and 100% 5 of dialkylamines. Such a substantially pure mixture also contains a percentage of monoalkylamines in the solvent which may vary between 0.01% and approximately 20% by volume. More specifically, the monoalkylamines content may vary from less than 1% to about 10%. In some modalities, the percentage of monoalkylamines varies from about 5% to about 15%. In still other embodiments of this invention, the solvent contains less than 5% and preferably less than 1% by volume of monoalkylamines. Another embodiment of such a modified solvent is one which has an amount of trialkylamines that is less than a maximum of 50% by volume and preferably as low as 0% by weight. trialkylamines. In some embodiments, the amount of trialkylamines in the solvent is less than 40% trialkylamines. Another embodiment still contains less than 25% by volume of trialkylamines. A preferred embodiment contains less than 10% by volume of trialkylamines and preferably less than 5% by volume of trialkylamines. One modality The preferred one still contains less than 1% by volume of trialkylamines. Other solvents of this invention optionally contain a percentage of alcohols as small as possible, desirably from less than 25% by volume to about 0%. Another modality contains less than 10% in volume of alcohol, desirably less than 5% by volume and preferably less than 1% by volume of alcohol. For example, a desired modified solvent contains about 90% of a mixture of highly branched dialkyl amine isomers and about 10% trialkylamines. Thus, useful modified solvents may have small amounts of alcohol, monoalkylamines and trialkylamines, and still increase the efficiency of acetic acid production in the methods of this invention. An embodiment of a modified solvent can be prepared as described above, by modification of a commercial solvent, i.e. removing alcohols and monoalkylamines to create a modified solvent desired for the processes of the present invention as described above. The commercial product Adogen 283® (Witco Corporation) is a dialyzamine., ie di (tridecyl) amine or N-tridecyl-1-tridecanamine (CAS No. 5910-75-8 or 68513-50-8). Essentially, the Adogen 283® solvent is a complex mixture of isomers that can be classified as monoalkyl-, dialkyl- and trialkylamines. The Adogen 283® solvent has an average molecular weight of 395 and a total amine value of 144.0 and contains, for example, 0.29 percent alcohols, 5.78 percent monoalkylamine and 85.99 percent dialkylamine. The mass spectrometry analysis of the amines with higher boiling points of the Adogen 283® solvent is shown in Table 1 below.

TABLE I Although this Adogen 283 solvent is recognized as a useful extraction solvent for extracting dilute acetic acid from aqueous phases, until the present invention, the technique recognized that, when the Adogen 283® solvent was distilled, it would substantially degrade, ie approximately 40% it was converted into undesired amides by reacting the amine with acetic acid for a period of 3 hours under distillation conditions [J. W. Althouse and L. L. Tazlarides, J. Indus. Eng. Chem. Res. 31: 1971-1981 (1992)], thus making it undesirable for acetic acid recovery processes involving distillation. Based on the above report, alcohols of the Adogen 283® solvent can also react with acetic acid at distillation temperatures to form esters. In addition, Adogen 283® solvent or modifications thereof, even in combination with a cosolvent, have been rejected for a process involving distillation, because of its undesirable amide formation [N. L. Ricker et al., J. Separation Technol .. 1: 36-41 (1970)].

Thus, a fundamental aspect of the present invention was the determination by the inventors of a method for modifying a solvent, such as the Adogen 283® solvent, which has a high distribution coefficient (v. .gr. Kd greater than or equal to 5 and preferably between about 10 and 20) 5 to eliminate its undesired characteristics. A further aspect of the invention is the combination of the modified solvent with a selected cosolvent, for a solvent mixture suitable for the acetic acid recovery process involving distillation. Modification of the Adogen 283® solvent is carried out to eliminate or reduce The percentages of alcohols and monoalkylamines are substantially as follows. The commercial solvent is subjected to distillation, preferably in a cleaned film evaporator and the distilled solvent is then subjected to an acid washing step. The acid washing step is carried out at room temperature, preferably using an organic acid diluted to a pH of less than 5. An exemplary acid is dilute acetic acid (at about 1-50 g / l, preferably at less than 30 g / l and more preferably at less than 3 g / l). The acid is generally used in a ratio of the diluted acid to the solvent of at least 1: 1. A preferred ratio is about 5: 1 of the acid with the solvent. These two steps of distillation and acid washing remove organic materials with low boiling points and monoalkylamines. Preferably, "low boiling point" is intended to mean less than about 115 ° C, preferably less than 100 ° C, to about 70 Torr.

%.? Xets .. J? -. ^ .'tjAi > ^^ »s« ^^ '^ a «fei & < ! i »-? Asa» J. -^ M * US ^ ~ - & In a specific example, the distillation was carried out in a cleaned film evaporator, with a feed rate of 56.4 g of Adogen 283® solvent / hour, a temperature of 164.3 ° C and a pressure of 69.9 Torr. The alcohols and the monoalkylamines are separated and are eliminated in the upper part of the distillation column by this procedure, leaving the resulting modified solvent containing a mixture of highly branched dialkylamines and trialkylamines to be eliminated in the lower part of the column of distillation. This modified solvent was referred to as modified solvent A. Modified solvent A was characterized as containing 0.02 percent low boiling organic materials, 0.16 percent monoalkylamines, 90.78 percent dialkylamines, and 9.04 percent trialkylamines. Table II provides a comparison of the fractions (in percentages) that make up the unmodified Adogen 283® solvent, the modified solvent A, and the fractions removed as a result of the procedure described above.

TABLE II This most preferred modified solvent A has an extraction coefficient of about 10 or higher and contains, among other components, a mixture of highly branched dialkyl amine isomers., modified to substantially reduce the alcohol content and the amount of monoalkylamines thereof. The modified solvent A is an excellent acetic acid concentrating solvent, particularly for use in the methods of this invention. The extraction coefficient of this modified solvent increases as the concentration of acetic acid decreases. The modified solvent A can then be further purified to still provide another desirable modified solvent, to which reference is made as modified solvent B. The modified solvent A is introduced into another distillation column under the same conditions as before. This distillation makes it possible to distill and eliminate the dialkylamines in the modified solvent A, at the top of the distillation column, resulting in the modified solvent B, while removing the trialkylamines in the lower part of the column. The modified solvent B is characterized by an extraction coefficient that is slightly better (greater than 10) and even better yield in the methods of this invention when combined with a selected co-solvent. Based on the teachings herein related to the modification of the Adogen 283® solvent and the modified solvents A and B, it is anticipated that other conventional solvents containing isomeric mixtures of highly branched dialkylamines may similarly be treated. 10 With some trialkylamines, together with monoalkylamines, alcohols and other components, such as Amberlite LA-2, P.M. = 375 [Rohm & Haas] and others mentioned in H. Reisinger and CJ King Ind. Eng. Chem. Res., 34: 845-852 (1995), to substantially eliminate alcohols, monoalkylamines and, if desired, trialkylamines, as described herein in order to create 15 solvents for use in processes involving extraction and distillation of acids from aqueous phases. One skilled in the art can easily apply this teaching to other such solvents without unnecessary experimentation. Another aspect of this invention involves a mixture of a modified solvent of this invention with a selected cosolvent, which mixture also has preferred characteristics for use in extraction and distillation processes for the recovery of acetic acid. You can select a wide variety of different cosolvents of alcohol to mix with the modified solvents identified above, as well as with the commercially available Adogen 283® solvent. Because of the high coefficient of distribution that is possible with the use of the Adogen 283® solvent and modified versions thereof, a wide variety of cosolvents can be employed in these mixtures. The solvent merely decreases the Kd in proportion to the fraction of cosolvent employed in the mixture. As an example, a mixture of 50% solvent Adogen 283® or a modified version thereof and 50% co-solvent of any type has half the Kd of Adogen 283® solvent. Although the phenomenon is true with other amine-based solvents, e.g. Alamine 336® solvent, Adogen 381® solvent, Adogen 260® solvent, among others, the Kd values for these pure solvents are very low (from 1 to 3), so dilution with cosolvents results in uneconomically low Kd values (from 0.5 to 1.5 or less). In the use of other solvents, such as the solvent Alamina 336®, Adogen 381® solvent, etc., the cosolvent must be chosen carefully to enhance the distribution coefficient. Although the Kd is dependent on the acid concentration in the fermentor (usually around 3-6 g / l), the desired Kd of the solvent mixture is desirably between about 1 and 20. For an acid concentration of about 4.5-5.5 g / l, the K of the solvent mixture is desirably between about 8 and 11. Another Kd of the solvent mixture is about 6-20. However, other values may be used for the coefficient in the practice of this invention. yes, "-» "- • '- - - s ** - ^ - ** .. - > . * .rJaX m & * ,. i ^ r ^? ^ ^ i ^ e ^ ssstíE & ^ i ^? ^^ S? ^ x - > ^ * .. - This solvent / cosolvent mixture must be immiscible with water and easily separated from water at reduced temperatures. The selected cosolvent must have a boiling point lower than that of the commercial solvent or the modified solvents described above. For example, a preferred cosolvent boils between 125 ° C and 250 ° C. More preferably, the preferred cosolvent boils between 150 ° C and 200 ° C. In one embodiment, the cosolvent boils at about 165 ° C. Alcohols should be avoided in the selection of a cosolvent because they react with acetic acid to form esters and also cause emulsification. The selected cosolvent can improve the physical properties, such as the viscosity of the mixture and can also help in reducing the boiling point of the solvent. One skilled in the art can make the selection of suitable cosolvents, also taking into account that cosolvents of low toxicity are essential for any solubility in water and return to the fermenter, and where the cosolvent will come into contact with the bacteria. A preferred cosolvent for use in the solvent mixture of this invention is one that forms an azeotrope (ie, a mixture that does not readily separate and behaves "as such") with water and acetic acid when in the form of vapor. The azeotrope-forming cosolvent enhances the volatility of at least one of the components, e.g. Water. The formation of an azeotrope allows the cosolvent and water with acetic acid as steam to move together (essentially as one) up and out of the top of a distillation column. When k? condenses the vapor, separates the cosolvent and water with the acetic acid. In the dehydration procedures described above, this allows the cosolvent to decant and return to the first distillation column. The acetic acid and water (and a little residual co-solvent) can then be continued on a second column for acetic acid recovery. The main advantage of an azeotrope-forming cosolvent is that it allows the recovery of acetic acid in two distillation columns instead of the three required for cosolvents that do not form azeotropes. Some cosolvents that exhibit the required characteristics include the cosolvents of low-boiling hydrocarbons that form azeotropes with acetic acid. Particularly desirable cosolvents that are suitable for this description include alkanes, particularly those in the range of C-9 to C-11. Among such useful co-solvents are n-nonane, n-decane, n-undecane, ethers and the Orfom® SX-18 ™ solvent (Phillips Mining, Inc.), that is, it is a mixture of C9-C11 soalkanes. Other cosolvents still useful for mixing with the modified solvents of this invention include solvents other than alcohol, among others listed in Table 3, page 1976 of Althouse (1992), cited above and incorporated herein by reference. Such cosolvents, when mixed with a modified dialkylamine solvent as described above, can reduce the boiling point of the solvent system, particularly when the solvent system is distilled in vacuo. The reduced boiling point also prevents or limits the formation of amide from the dialkylamine. Such a solvent / azeotrope-forming cosolvent mixture allows the distillation process to be carried out in two columns. Generally, the amount of the modified solvent in the solvent / cosolvent mixture can vary in the mixture from about 10 to about 90% by volume. Desirably, the amount of modified solvent containing dialkylamines of this invention is between about 30 and about 70% by volume of the solvent / cosolvent mixture. In preferred embodiments, the modified solvent is present in the mixture at about 60% by volume. At least 10% co-solvent is necessary to form a solvent / cosolvent mixture of this invention. The amount of co-solvent may vary from about 10 to about 90%, more desirably from about 30 to 70% by volume. In preferred embodiments, the modified solvent is present in the mixture at about 40% by volume. Thus, a preferred solvent / cosolvent mixture and exemplary of the present invention comprises 60% modified solvent A and 40% solvent Orfom® SX-18. It is expected that one skilled in the art can adjust the percentages of modified solvent and co-solvent, as desired for any particular distillation apparatus or process. Adjustments to the proportions of modified solvent to co-solvent to prepare a desired mixture will be based on factors, such as the identity and content of the modified and cosolvent solvent, their relative distribution coefficients, their viscosities, as well as practical considerations, such as heat availability, the size of the equipment and the relative costs of the two solvent components. For example, the best extraction coefficient seems to correlate with a high amine content, which increases the consumption of the solvent system. Thus, for some uses, high consumption would influence the desired proportions of the modified / cosolvent solvent. As an example, the SX-18 cosolvent proportionally reduces the distribution coefficient of the modified solvent mixture (eg 50% modified solvent A in solvent SX-18 has half the coefficient of distribution of 100% modified solvent A, but it is easier to work with it because of the decreased viscosity and the increased capacity to recover, due to the presence of the cosolvent. The cosolvent SX-18 boils between about 160 and 167 ° C and thus also lowers the boiling point of the mixture, thus reducing the amide formation. Expected that one skilled in the art has the ability to balance these factors to prepare any desired mixture of the modified solvent and the cosolvent. The desirable characteristics of the solvent / cosolvent mixtures of this invention harmonize with them for use in acetic acid extraction and distillation processes. For extraction, the desirable properties of the solvent mixture of this invention include a high extraction coefficient (i.e. about 3 or more and preferably about 10 or more), water immiscibility, good water / solvent separation, low toxicity to the bacterial culture, a clear difference of viscosity and density of the water, and good selectivity for the acetic acid over the other fermentation products, such as ethanol, salts and water . For distillation, the desirable properties of the solvent and the solvent mixture of this invention include, for example, a different boiling point difference between acetic acid (i.e., 118 ° C) and the cosolvent (e.g. ° C). These differences are also useful in the performance of the methods of this invention, because the greater the differences between the boiling points of these components, the distillation column may be smaller, resulting in improvements in efficiency and cost in acetic acid recovery processes. Significantly, the use of the modified / cosolvent solvent mixtures of this invention involves only losses of negligible solvent, due to thermal or reactive degradation, eg. oxidation. See, e.g., Figure 4 and Example 2. The solvent and the cosolvent are also characterized by limited reactivity with acetic acid, media components, biomaterials and other unknowns in the aqueous phase or the broth and the low miscibility in the water. Desirably, the The method of this invention for using the solvent / cosolvent substantially reduces or eliminates any tendency for acetic acid and solvent / cosolvent to form undesired byproducts, such as amides that could be formed by a reaction involving the amines in the novel modified solvent and solvent of this invention. It is expected that one skilled in the art can easily modify the solvent / cosolvent mixture of this invention in light of the lessons of this specification and with respect to the knowledge available regarding the factors indicated above. It is believed that such modifications are encompassed by the appended claims.

B. Use of novel solvent / cosolvent mixtures in the Recovery of Acetic Acid The methods of this invention employ the modified solvent / cosolvent mixtures described above and the particular process steps to avoid the formation of undesired amides. The use of modified / cosolvent solvent mixtures allows for improved recovery of acetic acid from aqueous phases, either in non-fermentation processes or microbial fermentation processes. Thus, according to one embodiment of this invention, a non-fermentation process for obtaining acetic acid from an aqueous phase can employ the modified / cosolvent solvent mixtures described above. Such The process employs as a first step to continuously contact the aqueous phase with a solvent mixture comprising a modified dialkyl amine / cosolvent solvent mixture as described above, to allow the acetic acid to be extracted from the aqueous phase to the phase solvent. This step can employ conventional extraction devices, such as columns, mixing and settling tanks, and similar devices designed for extraction and well known in the art. Additionally, the extraction conditions can be optimized also resorting to the teachings of the technique. The extraction temperature is desirably room temperature, i.e. from about 20 ° C to about 80 ° C. At about 80 ° C, essentially all carbon dioxide is recovered from the solvent, but the extraction is still effective. After that, the acetic acid is distilled from the solvent phase at distillation temperature which reduces the conversion of the amines of the solvent to the amides. The distillation temperature, as used herein, means the temperature in the lower part of the column. According to the invention, the distillation temperature can vary from about 115 ° C to about 160 ° C to reduce amide formation. Very significantly, the processes of this invention that the distillation temperatures are below 130 ° C to limit amide formation, while allowing the recovery of acetic acid. In a preferred embodiment, the distillation step is carried out in an oxygen-free vacuum, which also serves to reduce the temperature to minimize the amide formation and the oxidative degradation of the solvent or the solvent / cosolvent mixture. The higher the vacuum (ie lower absolute pressure), the lower the temperature and the lower the Amide formation and oxidative degradation. Desirably, a vacuum of less than 0.703 kg / cm2-absolute is required for this step. Preferably, vacuum is selected between 0.00703 kg / cm2 absolute and 0.3515 kg / cm2 absolute for the distillation step. More preferably, a vacuum of 5 0.2812 kg / cm2 absolute or less is useful in this distillation step to enhance the recovery of acetic acid. As a further advantage of the use of the modified azeotrope-forming solvent / cosolvent mixture of this invention is the use of two distillation columns to enhance the acetic acid recovery efficiency of the aqueous phases compared to the prior art methods. The distillation temperature control can be effected in the methods of this invention to limit solvent degradation, by a combination of factors, such as the selection of the cosolvent, the ratio of the solvent to the cosolvent and the vacuum conditions for the solvent. distillation step. Given the teachings of this specification, one skilled in the art can select the appropriate combination of factors to control the distillation temperature as required. For example, one skilled in the art can easily adjust the temperature and vacuum conditions of the distillation step within the above ranges to achieve A desired efficiency of acetic acid recovery, while minimizing amide formation and oxidative degradation of the solvent according to this invention. Such modifications are encompassed within the appended claims.

According to another embodiment of this invention, an anaerobic microbial fermentation process for the production of acetic acid employs a modified solvent / cosolvent mixture of this invention to enhance the efficiency of acetic acid recovery. In this process, a fermentation broth is formed which contains, among other components, acetic acid, fermenting in a bioreactor with a microorganism, an aqueous stream comprising a source of nutrients and a gas containing various mixtures of carbon monoxide, or carbon dioxide or hydrogen. Thus, in one embodiment, the gas stream contains carbon monoxide. In another embodiment, the gas stream contains carbon dioxide and hydrogen. In still another embodiment, the gas stream contains carbon dioxide, carbon monoxide and hydrogen. In still another embodiment, the gas stream contains carbon monoxide and hydrogen. Desirably such gases can be obtained at from waste gases from various industrial processes. Also, as mentioned, in the fermentation broth is an anaerobic acetogenic bacterium and a nutrient medium necessary for the growth of the bacteria. The anaerobic bacterium can be a strain or a mixed culture that contains one or more acetogenic bacteria, including, without Limitation, Acetobacterium kivui, A. Woodii, B? Tybacterium methylotrophicum, Clostridium aceticum, C. Acetobutylicum, C. Formoaceticum, C. Kluyveri, C. Thermoaceticum, C, Thermocellum, C. Thermohydrosulfuricum, Eubacterium limosum, Peptostreptococcus productus and C. Ljundahlii, and mixtures of same. Particularly desirable acetogenic bacteria are those strains previously discovered by the inventors, namely, C. Ljundahlii strain PETC ATCC 55383, strain O-52 ATCC 55989, strain ER12 ATCC55389 and strain C-01 ATCC 55988, and mixtures thereof. These acetogenic bacteria are generally obtainable from depositories, such as American Type Culture Collection, 10801 University Boulevard, Manassas, VA 20110-2209, or from commercial or educational institutions. The microorganisms identified above, discovered by the inventors, are deposited according to the Budapest Treaty for the Deposit of Microorganisms for Patent Purposes and such deposits comply with all requirements thereof. Nutrients are fed continuously to the fermenter. The nutrient media useful in such a fermentation broth are conventional and include those nutrients that are known to be essential for the growth of such acetogenic bacteria. An exemplary formation of nutrient medium (medium A plus medium B) for the growth of acetogenic bacteria at atmospheric pressure and which is sulfur-based is illustrated in the following Table III. However, many different nutrient media formulas can be used with components of differing concentrations. A One skilled in the art can readily formulate other nutrient media suitable for the methods described herein. The formula in Table III is merely an adequate formulation.

TABLE III Medium A Medium B twenty One skilled in the art can easily make the selection of the nutrients and other conditions for the fermentation by resorting to the existing knowledge and depends on a variety of factors, such as the microorganism used, the size and type of the equipment, the tanks and columns used, the composition of the gas stream or energy source, etc. One skilled in the art can easily select such parameters, in view of the teachings of this invention and is not a limitation of this invention. As the fermentation occurs, the exhaust gas containing unreacted inert gases and substrate is released, and the fermentation broth or liquid effluent is passed to a centrifuge, a hollow fiber membrane or other solid separation device and liquids to extract the microorganisms that are dragged and preferably return them to the fermenter. After that, the essentially cell-free aqueous stream of the fermentation broth (hereinafter in the present "cell-free stream") is subjected to extraction with the modified solvent / cosolvent mixture in an extractor. The ratio of the solvent to the material fed (ratio of the volume of solvent to the volume of cell-free current) can vary significantly from almost 0 to 10, for example. The lower the ratio of the solvent to the fed material, the higher the concentration of acid in the solvent and the lower the solvent requirements. In accordance with this invention, a solvent comprising a mixture of highly branched dialkylamine isomers modified to remove the monoalkylamines and a selected cosolvent, e.g., is employed in the extraction step. a cosolvent hydrocarbon mixture of low boiling point described above. As described in the above embodiment, this extraction is maintained at a temperature between about 20 ° C and about 80 ° C, depending on the viscosity of the solvent mixture. This extraction step removes the acetic acid from the cell-free stream and allows separation of the acetic acid from the nutrient media and other materials in the aqueous phase (which are recirculated to the bioreactor) to a phase that includes the solvent, a very small amount of water and acetic acid. Additionally, some components, such as Se, Mo, W and S, are extracted from the medium into the solvent. Another step still in the process involves continuously distilling the acetic acid and the water component of the solvent and the water of the extraction product. To carry out this step, the solvent / acid / water solution passes to a first distillation column, where this solution is heated to a temperature that reduces the conversion of the amines in the solvent to amides. As described above, the distillation temperature should vary from 115 ° C to a maximum of about 160 ° C to allow the recovery of acetic acid, while limiting solvent degradation and amide formation. Preferably, the temperature of the distillation step does not exceed about 130 ° C, in order to avoid the formation of amide. A fundamental advantage of the present invention is that the extraction steps and Distillation occurs without substantially degrading the amine solvent to an amide, and thus enhances the efficiency of recovery of the acetic acid from the broth. If the solvent / cosolvent mixture of this invention employs an azeotrope-forming cosolvent, the distillation columns operate more effectively. The formation of an azeotrope allows the cosolvent and the acid / water to move together (essentially as one) towards and away from the top of the first distillation column during the distillation step. In the liquid form, the cosolvent and the acetic acid / water are separated. Once separated, you can reintroduce the cosolvent to the column distillation. The acetic acid and water (and part of the residual cosolvent) then pass to a second distillation column where the cosolvent once again forms an azeotrope with water and acid, and all three components flow as steam out from the top of the column. the spine. The steam condenses and most of the water is refluxed. liquid. Since the condensed liquid contains a small amount of co-solvent, a small current is continuously returned to the solvent distillation column. The acetic acid product is extracted just above the first theoretical stage, ie the portion of the column in which the solvent and the acid are separated. A preferred embodiment of this method involves carrying out the distillation step under an oxygen-free vacuum, which also serves to reduce the temperature and prevent oxidative degradation of the solvent or the solvent / cosolvent mixture. The higher the void (ie ^^^^^^^^^^^^^^^^ a * ^^ ^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ oxidative As described above, the vacuum is less than 0.703 kg / cm2-absolute. Desirably, a vacuum of between 0.00703 kg / cm2 absolute and 0.3515 kg / cm2 absolute is useful in the distillation step. More preferably, a vacuum of 0.2812 kg / cm2 absolute or less is useful in this distillation step to further reduce the boiling point of the solvent / acid / water mixture, further reducing amide formation and enhancing acid recovery. acetic. As an additional advantage still of the use of the solvent mixture The modified / azeotrope-forming cosolvent of this invention is the use of two distillation columns to effect recovery of the acetic acid from the aqueous phases compared to the prior art processes. It is possible to carry out the control of the distillation temperature in The methods of this invention for limiting solvent degradation, by a combination of factors, such as the selection of the cosolvent, the ratio of the solvent to the cosolvent and the vacuum conditions for the distillation step. Given the teachings of this specification, one skilled in the art can select the appropriate combination of factors for control the distillation temperature as required. For example, one skilled in the art can easily adjust the temperature and vacuum conditions of the distillation step within the above ranges to achieve .. rfj__sft "« * - -.. imX ~ - »" '"*? ~ - < fe- > - H-V _ * »_._- saiafcfc-. * »*. _ »__. * «-. *. JBfc a_ié¡iStÍ _ * _ tt? »«. ix & & ^ z iS ^ a desired efficiency of recovery according to this invention. Such modifications are encompassed within the appended claims.

C. Extractive fermentation and direct contact extraction method According to yet another embodiment of this invention, the novel modified / cosolvent solvent mixtures described above are useful in a "direct contact extraction" and "extractive fermentation" process, it is say modifications of the anaerobic fermentation production process for the recovery of the acetic acid described above. The modifications of the process allow the production of acetic acid by means of a microbial fermentation without the need for a separation of bacterial cells before extraction or distillation. further, these solvent mixtures when used in microbial fermentation of acetic acid can eliminate the need to use a separate extractor. In addition to reducing the complexity of the process, this invention reduces the capital, operation and maintenance costs of the equipment necessary to perform the process of producing acetic acid, as well as the time to obtain the product. Thus, the "extractive fermentation" method of the invention provides an anaerobic microbial fermentation process for the production of acetic acid, which is a modification of the process described above. As a first step, the bioreactor or A fermentor containing anaerobic acetogenic bacteria in a mixture of suitable nutrient necessary for the growth of the bacteria is contacted with the modified solvent / cosolvent mixture described above at about 37 ° C and at least at one atmosphere of pressure (see FIG. say, 1.0344 kg / cm2 absolute) for a sufficient time to acclimate the bacteria to the presence of the solvent, ie to allow the bacteria to grow in the presence of the solvent. The anaerobic bacteria can be a strain of bacteria or a mixed culture that contains 12 or more strains of acetogenic bacteria; the bacterial strains listed above in part B may also be useful in this modification of the invention. Since many solvents are toxic to bacterial growth, this aspect of the invention that involves direct contact between the bacteria and the solvent reflects the acclimation of the cells to the solvent mixture, which is obtained by gradually increasing the contact between the cells and the mixture of solvent over time. Subsequently, an aqueous stream comprising a source of nutrients is introduced, and a gas containing several mixtures of carbon monoxide and carbon dioxide or hydrogen in the fermenter. Thus, in one embodiment, the gas stream contains monoxide carbon. In another embodiment, the gas stream contains carbon dioxide and hydrogen. In another embodiment, the gas stream contains carbon dioxide, carbon monoxide and hydrogen. In another embodiment, the gas stream contains carbon monoxide and hydrogen. In the same way, these gases they can be obtained from industrial waste gases. According to this step, a fermentation broth is formed which contains, among other components, acetic acid, solvent, bacterial cells and water.Nutrients are added continuously to the fermenter.The selection of particular nutrients, media and other conditions of temperature and pressure, etc., for fermentation can easily be made by one skilled in the art given the teachings of this invention, and depends on a variety of factors, such as the microorganism used, the size and type of the equipment, tanks and columns employed. , the composition of the current of gas or energy source, the gas retention time and the retention time of the liquid in the fermenter, etc. These parameters can be easily balanced and adjusted by one skilled in the art and are not considered as limitations of this invention. While fermentation occurs, discharge gases are released containing inert gases of unreacted substrates. In the fermentation broth, the presence of the solvent continuously separates the acetic acid and a small amount of water in a lighter "solvent phase" from the heavier bacteria and nutrient medium and other heavier materials in the aqueous phase. The mixture of the cell-solvent free stream is passed continuously to a sedimentation tank, in which the lighter solvent phase is decanted from the heavier aqueous phase with the sole action of gravity. Other solid-liquid separation methods are not used. The heavier phase is recirculated to the bireactor / fermentor; and the lightest phase which includes the solvent, a small amount of water and the acetic acid solution passes to a first distillation column. As described above, this solution is heated to a temperature for the recovery of acetic acid which minimizes the conversion of the amines in the solvent to amides. Preferably, the temperature of the distillation does not exceed about 160 ° C, and most preferably 130 ° C, in order to avoid the formation of amides. A key advantage of the present invention is that the distillation steps occur without substantially degrading the solvent amine to an amide, and thereby improving the efficiency of acetic acid production. When the solvent / cosolvent mixture of this invention employs azeotrope-forming cosolvent, the distillation columns used in the procedure work more efficiently. The formation of an azeotrope allows the cosolvent and the acid / water to move together (essentially as one) up and away from the top of the first distillation column during the distillation step. In the liquid form, the cosolvent and the acetic acid / water are separated. Once separated, the cosolvent can be reintroduced into the distillation column. Acetic acid and water (and some residual cosolvents) then pass through a second distillation column where the cosolvent again forms an azeotrope with water and acid, and all three components flow like a vapor out of the top of the column. The vapor condenses and most of the liquid is refluxed. Since the condensed liquid _ £. j ??? m &lXtg¡l ?? * > When you have a small amount of cosolvent, a small stream is continuously returned to the solvent distillation column.The acetic acid or product is extracted Just prior to the first theoretical stage, a preferred embodiment of this method involves carrying out the distillation step under an oxygen-free vacuum as described above, which also serves to reduce the temperature and prevent oxidative degradation of the solvent or solvent mixture. The higher the vacuum (ie, lower absolute pressure) the lower the temperature and amide formation and oxidative degradation Conveniently, a vacuum less than 0.703 kg / cm2 absolute, preferably between about 0.00703 kg / cm2 absolute and 0.3515 kg / cm2 absolute, and most preferably, a vacuum of 0.2812 kg / cm2 absolute or less is useful in this distillation step to further reduce the boiling point of the mixture that of solvent / acid / water, further reduce the formation of amide and improve the recovery of acetic acid. Another advantage of the use of the azeotrope-forming solvent / cosolvent mixture of this invention is the use of two distillation columns to achieve an improved acetic acid recovery efficiency of aqueous phases compared to prior art processes. The control of the distillation temperature in the processes of this invention to limit the degradation of the solvent can be achieved by a combination of factors, such as cosolvent selection, solvent and cosolvent ratio and vacuum conditions for the distillation step.

Given the teachings of this specification, one skilled in the art can select the appropriate combination of factors to control the distillation temperature as required. For example, one skilled in the art can easily adjust the temperature and vacuum conditions of the distillation step within the aforementioned scales to achieve the desired acetic acid recovery efficiency in accordance with this invention. Said modifications are included within the appended claims. In an optional "direct contact extraction" method of this invention, rather than removing cellular materials from acetic acid and water by filtration or centrifugation prior to extraction, all the fermentation broth containing the cells is introduced directly into an extractor . Among the conventional extraction devices are the columns with either the solvent phase or the aqueous phase as a continuous phase. These columns also have entrances and exits for solvent and culture of aqueous phase. The fermentation broth that includes the bacterial cells flows down through the column filled with solvent and the solvent flows upstream, countercurrent to the broth. Opposite flows can also occur with the column full of water. These columns differ depending on the type of packaging in the column and the sizes of it. Optionally, other extraction apparatuses, such as mixing and sedimentation tanks, can be used to perform the same tasks, and can be easily selected by a person skilled in the art without too much experimentation to perform this step as explained in the present. The presence of the solvent continuously separates the acetic acid and a small amount of water in the "solvent phase" from the more heavy phase containing bacteria and nutrient media, acetate salts, a small amount of acetic acid. and other heavier materials in the aqueous phase. The solvent phase containing acetic acid and a small amount of water is removed and continuously passed to a first distillation column, and then distilled as described in the immediately preceding embodiment. The aqueous phase containing the cellular materials leaves the bottom of extractor. Since the aqueous phase and the solvent phase are substantially immiscible, they naturally separate in the column, aided by the action of gravity. Other solid-liquid separation methods are not used. The heavier aqueous phase is recirculated to the bioreactor / fermentor. Any material The cell or protein formed in the culture / solvent interface is periodically removed from the extractor. Several speeds and directions of the solvent or water flows can be adjusted depending on the type of extractor selected. An example of the extractive fermentation method described The above is initially shown in Example 6. Examples of the direct contact extraction method are shown in Example 4, which employs a column filled with solvent and Example 5, which uses a column filled with water. The water-filled system is a less expensive option for a column full of solvent, which requires less solvent than the solvent-filled system. Both colotes are commercial options. It is expected that one skilled in the art can readily alter the specific conditions under which the extractive fermentation and direct extraction methods of this invention operate without departing from the scope of the invention.

D. Carbon dioxide stabilization According to another embodiment of this invention, the microbial fermentation process of a gas stream (particularly a gas stream containing carbon monoxide, carbon monoxide and hydrogen and optionally carbon dioxide, or carbon dioxide and hydrogen) to produce acetic acid or another product, for example, an alcohol, salt, etc., can be modified to increase its efficiency by substantially reducing the fermentation broth the presence of any carbon dioxide and optionally sulfur (in the form of hydrogen sulfide). In microbial fermentations of said gases, such as those of the prior art (see PCT WO98 / 00558) or those taught herein, carbon dioxide and hydrogen sulfide are present in both the gas stream leaving the fermenter / bioreactor as in the liquid fermentation broth that leaves the fermenter / bioreactor to the next stage of the process. For example, at 6 atmospheres of pressure in the fermenter (-5.2725 kg / cm2 gauge) the exit gas contains approximately 50% of CO2 and 700ppm of H2S, and the fermentation broth contains only 3 g / L of C02 and 0.01 g / L of H2S. During extraction, the solvent removes CO2 and H2S together with acetic acid. This is true for processes using conventional amine solvents, as well as for the use of the modified solvent / cosolvent mixtures described in this invention. Anything that is removed in the solvent reduces the solvent's ability to acid. Since the concentration of CO2 in the fermentation broth is similar to the concentration of acetic acid (5 g / L) in the fermentation broth, this represents a real threat to the Charge of acetic acid in the solvent. In this way, the CO2 present in the fermentation broth limits the charging potential of the solvent for acetic acid. Hydrogen sulfide is not a significant threat to the charge of acetic acid due to its low concentration, but H2S as a sulfide ion is an essential nutrient for the crop. The removal of sulfur from The fermentor in the fermentation broth also reduces the sulfur available to the bacteria in the fermenter. Although it appears that the reactor discharge gas has hydrogen sulfide and therefore is transporting itself sulfur, extracting the sulfur increases the cost of sulfur as a nutrient. In the same way, how carbon dioxide is required for the By converting hydrogen into acetic acid, its elimination in the fermentation broth during the production process reduces the use of hydrogen. t. nv? & tenSi, i- * «*» Jtr < »« Ay »_ 'ü_aSteMte.

Therefore, the present invention provides an improved method of microbial fermentation of gases for the production of acetic acid including as a process step the removal of carbon dioxide from the fermentation broth before extraction. One optional step, but convenient includes the removal of hydrogen sulfide from the fermentation broth before extraction. Preferably, both carbon dioxide and hydrogen sulfide are removed from the fermentation broth, and optionally returned to the fermenter. One modality of this procedure involves contacting the fermentation broth (which may be composed of bacterial cells, acetic acid, nutrient media, salts and other components of the fermentation) or the cell-free stream (which may have been filtered first or centrifuged to remove most of the bacterial cells and other heavier materials therein) with a stream of "stabilizer" gas devoid of carbon dioxide and preferably lacking hydrogen sulfide. This "stabilizing" gas can include, without limit, nitrogen, helium, argon, methane or the original diluted gas if it contains little to no carbon dioxide and preferably does not contain hydrogen sulfide. Basically any non-reactive gas or non-reactive gas mixture is useful in this context. The introduction of the stabilizing gas, for example, N2 to the fermentation broth or cell-free stream leaving the fermenter reverts the equilibrium between the dissolved CO2 (or H2S) in the liquid phase and gas phase, and stabilizes the gases in the liquid phase . The contact method preferred with the stabilizing gas is in a countercurrent stabilizer column. As well as equilibrium between the CO2 (or H2S) gas that is dissolved in the fermentation liquid leaving the fermenter, an equilibrium is also established between the broth or cell-free stream that enters the countercurrent column and the gas who leaves While the stabilizing gas and the fermentation broth loaded with CO2 or cell-free current make contact with each other, the equilibrium between the stabilizing gas, for example, N2 and the CO2 in the water is continuously updated. The packing in the column ensures a good surface between the liquid and the stabilizing gas. Although the liquid leaving the countercurrent column at the bottom has its CO2 concentration considerably reduced, the incoming fresh nitrogen stabilizer gas has a full capacity to achieve equilibrium with the CO2 in the water. When the nitrogen finally leaves the top of the stabilizing column it becomes saturated with CO2 (and H2S). The nitrogen loaded with CO2 (and H2S) can be purified to remove or recycle CO2 (and H2S) back to the fermenter. The "stabilized" or depurated fermentation broth or cell-free stream then enters the next step of the acetic acid production process, for example, solvent extraction or solvent contact in the direct extraction process described above, and distillation. See, for example, the schematic drawing of figure 3 and example 6A.

Another embodiment of this aspect of the invention is provided by altering the carbon dioxide stabilization method. As exemplified in example 6C, this procedure includes subjecting the fermentation broth (which may be composed of bacterial cells, acetic acid, nutrient media, salts and other components of the fermentation) or the cell-free stream (which may have been filtered or centrifuged first to remove most of the bacterial cells and other heavier materials in it) to a rapid pressure decrease before introduction to the extractor or in a solvent extraction column. For example, the pressure of the fermentation broth or cell-free stream can be lowered by 6 atmospheres (or more) at a lower pressure, for example, atmospheric pressure, which causes the carbon dioxide in the broth or cell-free stream get close to your equilibrium concentration. Preferably this pressure decrease occurs after the fermentation broth or cell-free stream leaves the fermentor and is in a separate container. The CO2 is preferably recirculated back to the fermenter. The "stabilized" fermentation broth or cell-free stream then enters the next step of the acetic acid production process, for example, solvent extraction or solvent contact in the above-described direct extraction process, and distillation . See, for example, example 6C.

Yet another embodiment of this aspect of the invention is provided by altering the carbon dioxide stabilization method. As exemplified in Example 6D, this procedure includes removing the fermentation broth (which may be composed of bacterial cells, acetic acid, nutrient media, salts and other components of the fermentation) or the cell-free stream (which may be first filtered or centrifuged to remove most of the bacterial cells and other heavier materials thereof) from the fermenter, and heat the broth or cell-free stream to a temperature of about 80 ° C, before extraction.

The high temperature causes the carbon dioxide in the broth or cell-free current to approach its equilibrium concentration. The CO2 and H2S are preferably recirculated to the fermenter by means of a variety of common engineering methods. The fermentation broth or cell-free current "stabilized" then enters the next stage of the acetic acid production process, for example, solvent extraction or contact with solvent in the direct extraction process described above, and distillation. See for example, example 6D. The only disadvantage of this modification of the procedure is that after the extraction, the The component of the aqueous broth can not be recirculated back to the fermenter, because the heating temperature kills the bacteria, and must be discarded. a '^^ »». «Faith f - ¿- - &X and - - -" ~ "- * - •" "* * * *., £ < It is expected that a person skilled in the art will alter the specific conditions under which stabilization of carbon dioxide and optionally hydrogen sulfide occurs away from the scope of this invention. The following examples illustrate several aspects of this invention and do not limit the invention, the scope of which is included in the appended claims.

EXAMPLE 1 Recovery of acetic acid from a stream of fermentation product using the solvent / cosolvent mixture of azeotropes of the invention A. 60% Solvent A Modified and 40% Co-solvent Orfom® SX-18 An apparatus and method for producing acetic acid from a variety of aqueous gaseous streams is described in detail in published international patent application No. PCT WO98 / 00558, included herein by way of reference. The process described there is modified according to one aspect of the present invention, as shown below. A stream of gas containing 45% carbon monoxide, 45% hydrogen and 10% carbon dioxide was introduced into a continuous stirred tank fermenter containing C. Ijungdahlii strain ER12 and a suitable nutrient medium. The liquid product stream of the fermenter with cellular recirculation (ie, cell separation using a hollow fiber membrane) that contained 5 g / l of free acetic acid and 5 g / l of acetate at a pH of 4.75 (ie, free cell current) was sent to a multi-stage countercurrent extraction column. In the extraction column, the cell-free stream was contacted with a solvent / cosolvent mixture of this invention containing 60% Modified Solvent A and 50% Orfom® SX 18 cosolvent at a temperature of 37 ° C and using a solvent of 0.09 (v / v) to feed the ratio. The solvent leaving the extractor contained 50 g / l of acetic acid, and the aqueous stream (which was sent back to the fermenter as recirculation) contained 5 g / l of acetate and 0.5 g / l of acetic acid. The solvent stream that contained the solvent The modified / cosolvent and acetic acid was sent to a distillation system containing a first "solvent" column, an accumulator and a second "acid" column. In the operation of the first distillation column, the combination of a low boiling co-solvent and a vacuum at a pressure of 0.3 atm allows the temperature of the column to be minimized and allows the separation of acid, water and co-solvent in the distillate of Modified Solvent A and a little co-solvent, which remains at the bottom of the column. The bottom temperature is maintained at a maximum temperature of 130 ° C per vacuum action. The modified solvent and co-solvent at the bottom of The column is sent back to the extractor as recirculation. The mixture at the top of the column, ie water, acetic acid and a little co-solvent, is separated at the top of the column and cooled to allow the co-solvent to condense and separate from the water / acid. . 5 By removing most of the cosolvent from the water / acid, the lowest concentration of the cosolvent in the water / acid is below the azeotrope. This mixture, which contains acetic acid and water and a small amount of co-solvent, is sent to the second "acid" distillation column. In this second column, the water and co-solvent and a little acid come out of the top of the column and the acetic acid goes to the bottom which has a temperature of 118 ° C. Part of the water / acid phase is refluxed into the column and the remaining water / acid and co-solvent phase recirculated back to extraction. The glacial acetic acid is removed near the bottom of this column as a product, and the distillate is sent back to the process as recirculation.

B. 30% Adoxane 283® LA (Witco) v 70% cosolvent SX-18 As another example of a fermentation method conducted in accordance with the present invention, the liquid product stream described in part A containing 5 g / l of free acid and 10 g / l of acetate at a pH of 5.0 was contacted with a solvent mixture containing 30% Adonge283®LA (Witco) solvent and 70% cosolvent SX-18 in a -. < ? - = ¿, «& > * _ "* .. ..and..a- ~ a?« »A.w .. -« «_ - - _. - * & - '»'" ** Staa ** ^ ti_ ^ £ ^ £, 2? L multi-stage extractor A solvent of 0.09 was used to feed the ratio \ The salient solvent d © [extractor contains 25 g / l of acetic acid and the aqueous stream contains 10 g / l acetate and 2.75 g / l acetic acid, thus the acid distribution coefficient is reduced by dilution with additional SX-18 cosolvent. The distillation is the same as described above.

C. 30% modified solvent A and 70% decanted co-solvent. An extraction similar to that of part B was carried out with 30% modified solvent A in a cosolvent, decane. The distribution coefficient remained the same as in part B, and the procedure for product recovery by distillation is equivalent.

D. 60% Adoaen 283® LA (Witco) solvent and 40% n-dodecane co-solvent The extraction of part A was carried out with 60% Adogen 283® LA (Witco) solvent in an n-dodecane cosolvent. The extraction procedure remained the same as in part B, producing 50 g / l of acid in the solvent, and 10 g / l of acetate and 0.5 g / l of acetic acid in the aqueous phase. The aqueous stream containing acetate is sent back to the fermenter as recirculation. The solvent stream containing acetic acid is sent to a distillation system very similar to the system , to iii. i ^ n cJtepsfc ». *Y ' . presented in part B, except that the pressure in the solvent column is 0.2 atmospheres and the temperature at the bottom of the column is 127 ° C.

EXAMPLE 2 5 Amide formation This example demonstrates the basis for the invention, that is, determination by the inventors that temperature control is vital for the efficient operation of a solvent containing amines in a The process for producing acetic acid when a solvent containing amines is used in the distillation and extraction steps. The formation of amide from amine in the solvent is an expression of first order velocity in the concentration of acetic acid illustrated with the formula: Y = kX, where Y represents the concentration of amide after 16 hours, measured in percentage by weight; X = concentration of acetic acid after 16 hours, measured in percentage by weight, and k = the amide formation rate constant. The velocity of amide formation and likewise the velocity constant, k, increases with temperature by an Arrhenius type 20 velocity expression, represented by the formula: 1 n (k) = -9163.21 (1 / T) + 27.41, where T = the absolute temperature in Kelvin.

Figure 4 illustrates a diagram of 1 n (k) as a function of the absolute absolute temperature that is used to find the Arrhenius velocity expression. For example, at a temperature of 150 C (1 / T = 0. 00236), the dgf amida formation speed is 9 times greater than at a temperature of 110 ° C (1 / T = 0.00261) EXAMPLE 3 Direct extraction of acetic acid using a continuous solvent phase column The fermentation broth obtained from a fermenter similar to that of example 1 contained 2.6 g / l of cells (dry weight), excess nutrients, 5 g / l of acetic acid and 5.0 g / l of acetate at a pH of 4.75. This broth is sent to a continuous solvent phase extraction column containing 60% Adogen 283® LA (Witco) solvent in SX-18 cosolvent. The extraction column is a cylindrical column, with or without packing, which has inlets and outlets for solvent and aqueous phase culture. The crop flows down through the column full of solvent, and the solvent flows in ascending form, against the flow of the crop. The solvent leaving the column contains 50 g / l of acetic acid and is sent to distillation for the recovery of acid before recirculating it back to the column. The outflow culture stream at the bottom of the column contains 5.0 g / l acetate, 0.5 g / l acetic acid, cells and nutrients and is sent to the fermenter as recirculation. Since the solvent and culture are immiscible, from little to 7, no water (culture) is present in the solvent and from little to no solvent it is present in the recirculated culture stream. A small layer of debris consisting of cellular proj- um material is formed at the culture / solvent interface and should be removed periodically.

EXAMPLE 4 Extraction of acetic acid using a continuous aqueous phase column 10 The fermentation broth of Example 3 is passed through an aqueous phase extraction column containing 60% Adogen solvent 283® LA (Witco) in cosolvent SX-18. The column is constructed in a similar to that in Example 3 except that the column is filled with culture from aqueous phase instead of solvent. Again the solvent and the culture flow countercurrent, with the solvent coming out from the top of the column and the crop leaving the bottom of the column. The aqueous phase and solvent phase salient concentrations are the same as in Example 3. bu? jsA'i a * ^ .JyX a ^ aa s a ».

EXAMPLE 5 Internal extractive fermentation for the production of acetic acid from CO, CO? and H? Industrial waste gas containing 7.52% carbon dioxide, 31.5% carbon monoxide, 27.96% hydrogen and 33.02% nitrogen is fermented to acetic acid / acetate at a pH of 5.0 in a fermenter / reactor as described in Example 1A, using Clostridium Ijungdahlii, isolated BRI ERI2. The gas retention time (ratio of reactor volume and gas flow rate) is 10 minutes and the liquid dilution rate (ratio of average liquid flow rate and reactor volume) is 0.03 hour "7 The medium which contains essential vitamins and minerals flows continuously into the reactor.The stirring speed is 1000 rpm.The reactor also contains a solvent phase of 60% Modified Solvent A of this invention in SX-18 cosolvent.When the culture produces acetic acid a The solvent is extracted from CO, CO2 and H2. A mixture of solvent and culture leaves the fermenter and separates in a small sedimentation tank, a portion of the aqueous phase, equal in velocity at the average feed rate, flows from the system as a waste gas The equilibrium of the aqueous phase of the separator is returned to the reactor The solvent containing extracted acid is sent to distillation for recovery After recovery the solvent is recycled to the reactor. _ - _. *. ^ Bk & & EXAMPLE 6 Culture stabilization before acid extraction A.- Nitrogen stabilization 5 Reactor culture of examples 1 to 4 containing bacterial cells, 5 g / l of acetic acid, 9.3 g / l of acetate and dissolved sulfur and carbonate at a pH of 5.0 is passed through the reactor. a nitrogen stabilization column to remove the dissolved CO2 and sulfur as H2S before passing the culture through an extraction column. This operation is necessary to In order to prevent the solvent from being charged with C02 and H2S instead of acetic acid, and to return H2S as a source of sulfur and reducing agent back into the culture. The N2 gas stream containing H2S and CO2 is sent back to the reactor as a secondary gas supply. Using the nitrogen stabilizer, the solvent is charged to 50 g / l of acetic acid. Without the elimination of CO2 and H2S before extraction, the solvent is charged with 25 to 30 g / l of acetic acid.

B.- Stabilization with alternative gases The culture of part A is stabilized with gases other than N2 20, including methane or CO2-free synthesis gas containing H2, CO, CH. The other aspects of the example are the same.

C- Stabilization via pressure reduction for Wjf r CO? dissolved The pressure of the fermentation field in part A decreases rapidly by 6 or 3 atmospheres at atmospheric pressure in order to release. * 5 C02 before loading the extractor. The 'CO2 pressure in the crop approaches the equilibrium concentration according to Henry's law at one atmosphere, a fairly low level which helps to maximize the extraction of the acid by the solvent.

D.- Stabilization via preheating to release CO? Dissolved The cell-free stream from part A is pre-heated before extraction to release CO2 in a manner very similar to part C. The broth can not be reused after heating. All published documents are incorporated herein way of reference. Numerous modifications and variations of the present invention are included in the above-identified specification and are intended to be apparent to those skilled in the art. Said modifications and alterations to the compositions and methods of the present invention are presumed to be included in the scope of the attached claims.

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Claims (52)

NOVELTY OF THE INVENTION CLAIMS

1. - A solvent / cosolvent mixture immiscible with water comprising: (a) a solvent immiscible with water comprising more than 50% by volume of a mixture of highly branched dialkylamine isomers, and from about 0.01% to 20% by volume of monoalkylamine having said solvent a distribution coefficient greater than 10; and (b) at least 10% by volume of an alcohol-free cosolvent having a boiling point lower than the boiling point of said solvent (a), characterized in that said mixture extracts acetic acid from aqueous streams.

2. The mixture according to claim 1, further characterized in that said cosolvent is immiscible with water and is easily separated from it, and has a low toxicity to anaerobic acetogenic bacteria.

3. The mixture according to claim 1, further characterized in that said cosolvent forms an azeotrope with water and acetic acid.

4. The mixture according to claim 1, further characterized in that said co-solvent comprises a hydrocarbon having 9 to 11 carbon atoms.

5. - The mixture according to claim 1, further characterized in that said solvent (a) contains more than 80% by volume of dialkylamines and is reduced to less than about 1% by volume of low boiling compounds and monoalkylamines further characterized in that said compounds of low boiling boil at a temperature of or less than 115 ° C at 69.9 Torr.

6. The mixture according to claim 1, further characterized in that said solvent (a) contains from about 1% to 10% by volume of trialkylamines.

7. The mixture according to claim 1, further characterized in that said solvent (a) is produced by distillation of a solvent containing low boiling compounds, monoalkylamines, dialkylamines and trialkylamines all substantially low boiling compounds and monoalkylamines to improve the acetic acid extractor capacity characterized further because the low boiling compounds boil at a temperature of or less than 115 ° C to 69.9 Torr.

8. The mixture according to claim 7, further characterized in that said solvent (a) is produced by subjecting said distilled solvent to a second distillation to substantially reduce all trialkylamines.

9. A process for obtaining acetic acid from an aqueous phase comprising acetic acid comprising the steps of: (a) contacting the aqueous phase with the solvent / cosolvent mixture of

any of claims 1 to 8; (b) extracting acetic acid from said aqueous phase in the resulting solvent phase; and (c) distilling acetic acid from said solvent phase under a temperature not exceeding 160 ° C.

10. An anaerobic microbial fermentation process for the production of acetic acid, said method comprising the steps of: (a) fermenting in an bioreactor an aqueous stream comprising anaerobic acetogenic bacteria in a nutrient medium and a gas stream comprising at least one gas (or more) selected from the group consisting of (a) carbon monoxide, (b) carbon dioxide and hydrogen, (c) carbon monoxide, carbon dioxide and hydrogen, and (d) carbon monoxide and hydrogen; thus producing a fermentation broth comprising acetic acid; (d) separating the bacteria from the other components in said broth to provide a substantially cell-free stream; (c) continuously extracting acetic acid from said cell-free stream in a solvent phase by contacting said cell-free stream with a solvent mixture of any of claims 1 to 8; and (d) continuously distilling the product of (c) the acetic acid separately from the solvent phase under a temperature not exceeding 160 ° C; further characterized in that the extraction and distillation steps occur without substantially degrading the amine in an amide, thus improving the production efficiency of acetic acid.

11. The method according to claim 10, further characterized in that the separation step uses a centrifuge,

a hollow fiber membrane or a solid-liquid separation postpositive.

12. The process according to claim 10, further characterized in that it comprises as step (e) recirculating the solvent to the distillation device of step (d) and the cell-free stream to the bioreactor of step (a).

13. The method according to claim 10, further characterized in that the distillation step occurs in a substantially oxygen-free vacuum.

14. The process according to claim 10, further characterized in that step (d) further utilizes a vacuum between about 0.03515 to about 0.703 kg / cm2 absolute.

15. The process according to claim 10, further characterized in that the anaerobic bacterium is selected from the group consisting of Acetobacteri? M kivui, A. woodii, Butyribacterium methylotrophicum, Clostridium aceticum, C. acetobutylicum, C. formoaceticum, C. kluyverí, C. thermoaceticum, C. thermocellum, C. thermosaccharolyticum, Eubacterium limosum, Peptostreptococcus productus, and C. Ijungdahlii, and their mixtures.

16. The method according to claim 15, further characterized in that C. Ijungdahlii is selected from strains consisting of: PETC ATCC 55383, O-52 ATCC 55989, ER12 ATCC 55380 and C-01 ATCC 55988, and mixtures thereof .

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17. - A method for improving the efficiency of acetic acid recovery of a fermentation broth comprising an aqueous stream containing anaerobic acetogenic bacteria and nutrient media, said bacteria having been fermented in the presence of a gas stream comprising minus one gas selected from the group consisting of (a) carbon monoxide, (b) carbon dioxide and hydrogen, (c) carbon monoxide, carbon dioxide and hydrogen; and (d) carbon monoxide and hydrogen; said method comprising contacting said stream with a solvent mixture according to any of claims 1 to 8; continuously extracting acetic acid from said stream in the solvent mixture; and distilling the acetic acid from the solvent at a distillation temperature not exceeding 160 ° C, without substantially degrading the amine into amide.

18. An anaerobic microbial fermentation process for the production of acetic acid, said process comprising the steps of: (a) supplying in a fermenter an anaerobic acetogenic bacterium in a mixture of nutrients and a solvent mixture in accordance with any of the claims 1 to 8 for a time sufficient to acclimate the bacteria to said solvent; (b) introducing into the fermenter an aqueous stream comprising at least one gas selected from the group consisting of (a) carbon monoxide, (b) carbon dioxide and hydrogen, (c) carbon monoxide, carbon dioxide and hydrogen, and (d) carbon monoxide and hydrogen; and producing a fermentation broth comprising

said bacteria, nutrient media, acetic acid, solvent and water; (c) introducing the fermentation broth in a sedimentation tank, wherein an aqueous phase containing the bacteria and nutrient medium is sedimented to the bottom of the tank of the solvent phase containing acetic acid, solvent and water, without filtration; (d) continuously distilling the acetic acid from the solvent phase of part (c) separately from the solvent phase under a temperature not exceeding 160 ° C; wherein the distillation step occurs without substantially degrading the amine in an amide, thereby improving the efficiency of acetic acid production.

19. The method according to claim 18, further characterized in that it comprises recirculating the solvent and the aqueous phase containing bacteria in the fermenter.

20. The process according to claim 19, further characterized in that the distillation step occurs in a substantially oxygen-free vacuum.

21. The process according to claim 18, further characterized in that step (d) further employs a vacuum between about 0.03515 to about 0.703 kg / cm2 absolute.

22. The method according to claim 18

20 further characterized in that the anaerobic bacterium is selected from the group consisting of Acetobacterium kivui, A. woodii, Butyribacterium methylotrophicum, Clostridium aceticum, C. acetobutylicum, C. formoaceticum,

C. kluyveri, C. thermoaceticum, C. thermocellum, C. thermosaccharolyticum,

Eubacterium limosum, Peptostreptococcus productus, and C. Ijungdahlii, and their mixtures. The method according to claim 22, further characterized in that C. IjungdahJii is selected from strains consisting of: PETC ATCC 55383, O-52 ATCC 55989, ERI2 ATCC 55380 and C-01 ATCC 55988 , and its mixtures. 24. An anaerobic microbial fermentation process for the production of acetic acid, said process comprising the steps of: (a) fermenting in a bioreactor an aqueous stream comprising a

A nutrient mixture with an anaerobic acetogenic bacterium and at least one gas selected from the group consisting of (a) carbon monoxide, (b) carbon dioxide and hydrogen, (c) carbon monoxide, carbon dioxide and hydrogen; and (d) carbon monoxide and hydrogen; thus producing a broth comprising acetic acid, water and bacterial cells; (b) introduce

15 in an extraction device containing either a solvent phase or a continuous aqueous phase and having outlets and inlets, (i) said broth without cell separation and (ii) a solvent comprising a solvent mixture in accordance with the claims 1 to 8, further characterized in that the solvent phase containing acetic acid, solvent and water leaves the

20 separate extraction device of an aqueous phase comprising the bacteria and nutrient media; (c) distill continuously from the solvent phase of part (b) the acetic acid and water separately from the solvent at a temperature not exceeding 160 ° C; further characterized because steps (b) and (c)

? • *? _, - ^ 3? ^ G ^ a ^^ sfefeAt ^ Slg..ífe &. < They occur without substantially degrading the amine in amide, thus improving the efficiency of acetic acid production. 25. The process according to claim 24, further characterized in that step (b) comprises introducing the solvent into the extraction device in a parallel or countercurrent flow with respect to that of the broth. 26. The method according to claim 24, further characterized in that it comprises recirculating the solvent and the aqueous phase containing the bacteria in the fermenter. 27. The method according to claim 24 further characterized in that the distillation step occurs in a substantially oxygen-free vacuum. 28. The method according to claim 24, further characterized in that step (c) further employs a vacuum between approximately 0.03515 to about 0.703 kg / cm2 absolute. 29. The method according to claim 24, further characterized in that the anaerobic bacterium is selected from the group consisting of Acetobacterium kivui, A. woodii, Butyribacterium methylotrophicum, Clostridium aceticum, C. acetobutylicum, C. formoaceticum, C. kluyveri, C. thermoaceticum, C. thermocellum, C. thermosaccharolyticum, Eubacterium limosum, Peptostreptococcus productus, and C. Ijungdahlii, and mixtures thereof.

30. - The method according to claim 29, further characterized in that C JJ ngdahlii is selected from strains consisting of: PETC ATCC 55383, 0-52 ATCC 55989, ERI2 ATCC 55380 and C-01 ATCC 55988, and mixtures thereof. a 5 31.- A process of anaerobic microbial fermentation for the production of acetic acid, this method comprising the steps of: (a) fermenting in a bioreactor an aqueous stream comprising at least one gas selected from the group consisting of (a) ) carbon monoxide, (b) carbon dioxide and hydrogen, (c) monoxide

10 carbon, carbon dioxide and hydrogen, and (d) carbon monoxide and hydrogen; in a mixture of nutrient with an anaerobic acetogenic bacterium, thus producing a fermentation broth comprising acetic acid, and dissolved carbon dioxide; (b) removing the carbon dioxide from the fermentation broth before extraction; (c) contact the broth

15 (b) with a solvent comprising an amine for a sufficient time to cause the formation of a solvent phase containing acetic acid, solvent and water; (d) continuously distilling acetic acid from the solvent phase. 32. The process according to claim 31, further characterized in that the fermentation broth comprises sulfur

20 dissolved hydrogen, and further comprises removing the hydrogen sulfide from the fermentation broth before extraction. 33.- The method according to claim 31 or 32, further characterized in that the elimination step comprises putting in

contact the fermentation broth cort μn gas that does not contain carbon dioxide, oxygen or hydrogen sulfide. 34. The method according to claim 33, further characterized in that the gas further comprises another gas selected from the group consisting of nitrogen, methane, helium, argon, a non-reactive gas or mixtures thereof. 35.- The method according to claim 33, further characterized in that the elimination step occurs in a countercurrent stabilization column. 36.- The procedure according to claim 31 or

32, further characterized in that the elimination step comprises reducing the pressure in the fermentation broth in a container separated from the fermenter. 37.- The method according to claim 31 or 32, further characterized in that it comprises separating the bacteria from the other components in the broth to provide a substantially cell-free stream before the removal step. 38.- The method according to claim 37, further characterized in that the elimination step comprises heating the cell-free stream to approximately 80 ° C in a container separated from the fermenter.

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39. - The method according to claim 31, further characterized in that the solvent is the solvent mixture of any of claims 1 to 8. The method according to claim 39, further characterized in that the distillation step occurs at a temperature not exceeding 160 ° C, without substantially degrading the amine in amide, thereby improving the efficiency of acetic acid production. 41.- The method according to claim 31, further characterized in that it comprises recirculating the solvent and the bacteria in the fermenter. 42.- The method according to claim 39, further characterized in that the distillation step occurs in a substantially oxygen-free vacuum. 43. The process according to claim 40, further characterized in that the distillation step also employs a vacuum between about 0.03515 to about 0.703 kg / cm2 absolute. 44.- The method according to claim 31, further characterized in that the anaerobic bacterium is selected from the group consisting of Acetobacterium kivui, A. woodii, Butyribacterium methylotrophicum, Clostridium aceticum, C. acetobutylicum, C. formoaceticum, C. kluyveri, C. thermoaceticum, C. thermocellum, C. thermosaccharolyticum, Eubacterium limosum, Peptostreptococcus productus, and C. Ijungdahlii, and mixtures thereof.

. fc * & - ~ - *? rÍ ~ »- 45.- The procedure according to claim 44, further characterized in that C. Ijungdahlii is selected from the strains consisting of PETCC ATCC 55383, O-52 ATCC 55989, ERI2 ATCC 55380 and C-01 ATCC 55988, and mixtures thereof. 46. The method according to claim 31, further characterized in that contact with the solvent occurs in a countercurrent column. 47. An immiscible solvent with water modified useful in the extraction of acetic acid from aqueous streams comprising more than 10 50% by volume of a mixture of highly branched dialkyl amine isomers and from about 0.01% to 20% by volume of monoalkylamine, 48. The solvent according to claim 47 which is a modified form of Adogen 283® solvent, substantially reduced in its content of low boiling compounds and monoalkylamines. 49. The solvent according to claim 47 which is substantially purified from trialkylamines. 50.- A method to prepare a modified solvent that

20 comprises the steps of: (a) distilling an unmodified solvent comprising low boiling compounds, monoalkylamines, highly branched dialkylamines and trialkylamines, about 75 to about

100% of said low boiling compounds and approximately 80 to near

100% of the monoalkylamines, thus improving the effective acetic acid capacity of the solvent - distillate; further characterized in that the distillation of the low boiling compounds occurs at approximately a temperature of 100 to 160 ° C at approximately 70 Torr; and (b) washing the distilled solvent using an organic acid at an acid to solvent ratio of about 1: 12 to about 5: 1. The method according to claim 50, further characterized in that it comprises subjecting the solvent distilled to a second distillation to substantially reduce all trialkylamines 52. The solvent immiscible with water modified according to claim 47, further characterized by comprising about 85% to 91% by volume of a mixture of dialkylamine isomers highly branched and from about 0.01% to about 6% by volume of monoalkylamine, further characterized in that the mono and dialkylamines have from 12 to 14 carbon atoms, said solvent having a distribution coefficient of about 10 to about 20.

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